Commit e23ee747 authored by Kirill Tkhai's avatar Kirill Tkhai Committed by Ingo Molnar
Browse files

sched/rt: Simplify pull_rt_task() logic and remove .leaf_rt_rq_list 

[ Peter, this is based off of some of my work, I ran it though a few
  tests and it passed. I also reviewed it, and added my SOB as I am
  somewhat a co-author to it. ]

Based on the patch by Steven Rostedt from previous year:

https://lkml.org/lkml/2012/4/18/517



1)Simplify pull_rt_task() logic: search in pushable tasks of dest runqueue.
The only pullable tasks are the tasks which are pushable in their local rq,
and no others.

2)Remove .leaf_rt_rq_list member of struct rt_rq and functions connected
with it: nobody uses it since now.

Signed-off-by: default avatarKirill Tkhai <tkhai@yandex.ru>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/287571370557898@web7d.yandex.ru


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent d81344c5

kernel/sched/rt.c

+16 −66
Original line number Diff line number Diff line
@@ -399,20 +399,6 @@ static inline struct task_group *next_task_group(struct task_group *tg) 
		(iter = next_task_group(iter)) &&			\

		(rt_rq = iter->rt_rq[cpu_of(rq)]);)



static inline void list_add_leaf_rt_rq(struct rt_rq *rt_rq)

{

	list_add_rcu(&rt_rq->leaf_rt_rq_list,

			&rq_of_rt_rq(rt_rq)->leaf_rt_rq_list);

}



static inline void list_del_leaf_rt_rq(struct rt_rq *rt_rq)

{

	list_del_rcu(&rt_rq->leaf_rt_rq_list);

}



#define for_each_leaf_rt_rq(rt_rq, rq) \

	list_for_each_entry_rcu(rt_rq, &rq->leaf_rt_rq_list, leaf_rt_rq_list)



#define for_each_sched_rt_entity(rt_se) \

	for (; rt_se; rt_se = rt_se->parent)
@@ -509,17 +495,6 @@ typedef struct rt_rq *rt_rq_iter_t; 
#define for_each_rt_rq(rt_rq, iter, rq) \

	for ((void) iter, rt_rq = &rq->rt; rt_rq; rt_rq = NULL)



static inline void list_add_leaf_rt_rq(struct rt_rq *rt_rq)

{

}



static inline void list_del_leaf_rt_rq(struct rt_rq *rt_rq)

{

}



#define for_each_leaf_rt_rq(rt_rq, rq) \

	for (rt_rq = &rq->rt; rt_rq; rt_rq = NULL)



#define for_each_sched_rt_entity(rt_se) \

	for (; rt_se; rt_se = NULL)
@@ -1066,9 +1041,6 @@ static void __enqueue_rt_entity(struct sched_rt_entity *rt_se, bool head) 
	if (group_rq && (rt_rq_throttled(group_rq) || !group_rq->rt_nr_running))

		return;



	if (!rt_rq->rt_nr_running)

		list_add_leaf_rt_rq(rt_rq);



	if (head)

		list_add(&rt_se->run_list, queue);

	else
@@ -1088,8 +1060,6 @@ static void __dequeue_rt_entity(struct sched_rt_entity *rt_se) 
		__clear_bit(rt_se_prio(rt_se), array->bitmap);



	dec_rt_tasks(rt_se, rt_rq);

	if (!rt_rq->rt_nr_running)

		list_del_leaf_rt_rq(rt_rq);

}



/*
@@ -1394,42 +1364,24 @@ static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu) 
	return 0;

}



/* Return the second highest RT task, NULL otherwise */

static struct task_struct *pick_next_highest_task_rt(struct rq *rq, int cpu)

/*

 * Return the highest pushable rq's task, which is suitable to be executed

 * on the cpu, NULL otherwise

 */

static struct task_struct *pick_highest_pushable_task(struct rq *rq, int cpu)

{

	struct task_struct *next = NULL;

	struct sched_rt_entity *rt_se;

	struct rt_prio_array *array;

	struct rt_rq *rt_rq;

	int idx;



	for_each_leaf_rt_rq(rt_rq, rq) {

		array = &rt_rq->active;

		idx = sched_find_first_bit(array->bitmap);

next_idx:

		if (idx >= MAX_RT_PRIO)

			continue;

		if (next && next->prio <= idx)

			continue;

		list_for_each_entry(rt_se, array->queue + idx, run_list) {

	struct plist_head *head = &rq->rt.pushable_tasks;

	struct task_struct *p;



			if (!rt_entity_is_task(rt_se))

				continue;

	if (!has_pushable_tasks(rq))

		return NULL;



			p = rt_task_of(rt_se);

			if (pick_rt_task(rq, p, cpu)) {

				next = p;

				break;

			}

		}

		if (!next) {

			idx = find_next_bit(array->bitmap, MAX_RT_PRIO, idx+1);

			goto next_idx;

		}

	plist_for_each_entry(p, head, pushable_tasks) {

		if (pick_rt_task(rq, p, cpu))

			return p;

	}



	return next;

	return NULL;

}



static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask);
@@ -1703,12 +1655,10 @@ static int pull_rt_task(struct rq *this_rq) 
		double_lock_balance(this_rq, src_rq);



		/*

		 * Are there still pullable RT tasks?

		 * We can pull only a task, which is pushable

		 * on its rq, and no others.

		 */

		if (src_rq->rt.rt_nr_running <= 1)

			goto skip;



		p = pick_next_highest_task_rt(src_rq, this_cpu);

		p = pick_highest_pushable_task(src_rq, this_cpu);



		/*

		 * Do we have an RT task that preempts

kernel/sched/sched.h

+0 −1
Original line number Diff line number Diff line
@@ -361,7 +361,6 @@ struct rt_rq { 
	unsigned long rt_nr_boosted;



	struct rq *rq;

	struct list_head leaf_rt_rq_list;

	struct task_group *tg;

#endif

};

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